Antioxidant



Patented Dec. 26, 1944' ANTIOXIDANT Carlin F. Gibbs, Silver Lake, Ohio, assignor to The B. F. Goodrich Company, New York, N. Y., a corporation of New York No Drawing. Application October 15, 1943, Serial No. 506,426

14 Claims.

This invention relates to the preservation of organic materials which tend to deteriorate by the absorption of oxygen from the air, and pertains more specifically to the preservation of rubber by the incorporation therein of an antioxidant.

It has heretofore been proposed by Craig in- U. S. Patent 2,048,781, issued July 28, 1936, to

employ various aromatic substituted aminoindans as antioxidants. The patentee discloses as his preferred class those compounds in which the indan group is attached to the amino nitrogen at the 1- or alpha-position:

6 lCH-NH-Aromatiw /2 H2 4 C H:

The class of compounds disclosed is said to be' generally useful for the preservation of rubber and other organic materials which deteriorate by CH2 These compounds may be prepared, for example,

by making a 5-aminoindan by the method of Lindner and Bruhin, ;Berichte 60, 435, (1927).

The -5-aminoindan thus preparedmay then be condensed with a halogenated aromatic compound in order to give the desired product. Various substituents, such as alkyl, alkenyl, aryl, aralkyl, hydroxy, alkoxy and aryloxy groups may b present oneither the 5-indan or the aromatic group. 'It is generally desirable, however, to have noacidic group present, such as nitro, carboxyl, sulfonic, or the like.

Among the compounds which fall within the scope. of my invention are 5-(2-methylanilino) indan, 5-(4-hydroxyanilino) indan, l methyl-fianilinoindan, 2-methyl-5-anilino indan, B-methy'l-,-5-anllino indan, 1,2-dimethyl-5-anilino indan, 2,2-diethyl-5-anilino' indan, S-(beta-naphthylamino) indan, 5-(alpha-naphthylamino) indan,

di-(l-methyl-fi-indanamlne) til-(1,2 dimethyl- 5-indanamine) di-(2-methyl-5-indanamine) di- (l-isopropyl-E-indanamine) 1-methy1-di-(5-inranam'ine) 1,2-dimethyl-di-(B-indanamine) N- o (p-phenoxy phenyl) -5-indanamine, N-(o-phenoxy phenyl) 5 indanamine, di-(5-indan) -pphenylenediamine, and the like. The 5-(arylamino) indans are preferred.

The following specific examples will serve further to illustrate the nature of the preparation of my new compounds. 1 I

Example I The preparation of 5-ani1ino indan may be carriedvout by first preparing 5-aminoindan by the method of Lindner et al., 100. cit., and then condensing it with o-chlorobenzoic acid followed by decarboxylation. Although chlorobenzene may beused, in whichcase decarboxylation is unnecessary, it has been found that better results are obtained by following the above-described procedure. A mixture of 26.6 parts by weight of 5- aminoindan, 31.5 parts-of o-chlorobenzoic acid, and 32 parts of potassium carbonate was heated 25 to a temperature of about 160 C. in order to remove all water. It was then cooled to about 130 C., and 0.5 partof powdered copper was added. Upon heating'to 150 C., a" reaction occurred. Completion of the reactionwas ensured by gradually raising the temperatureto about 220 C.- over a period-of about 2 /2 hours. After cooling, 500 parts of water were added to the mixture, and the copper was removed by filtration. Upon acidification of the filtrate with acetic acid, a precipitate formed, which was collected and dried. The-product was readily decarboxylated by heating to 250 C. for '10 minutes. The resultant material, after distillation at reduced pressure, was reasonably pure 5-anilinoindan. If a. completely pure product is desired the material may be dissolved in-50 parts of benzene and the solution washed with several"portions of 5% aqueous sodium hydroxide solution. After re-- moval of the benzene by heating at atmospheric pressure, .the product may be redistilled at reduced pressure KB. P. 168-182 C. at 1 mm.). Recrystallization from hexane gives a white crystalline solid melting at 45 to 46 C. Analysis gives values corresponding'to those calculated for 5 -anilino indan.

Example-II Di-(5 indanaininel maybe prepared by condensing 5-aminoindan with 5-ch1oroindan. The

latter compound may be prepared from 5-aminoindan by the well-known Sandmeyer reaction as described in Organic Syntheses 3, 33 (1923). To 91 parts by weight of 37% aqueous hydrochloric acid there was added 32 parts of 5-amin0indan. The mixture was cooled to about C., and to it was added 16.8 parts of sodium nitrite dissolved in 48 parts of water.- This solution was. then added slowly and with stirring. to a 0.3 molar solution of cuprous chloride in hydrochloric acid at 0 C. After standing at room temperature for about two hours the mixture was heated to 60 C. in order to ensure completion of the reaction.

The product was then steam-distilled, dissolved in about 50 parts of benzene, washed with several portions of concentrated sulphuric acid, and finally with water. The benzene was removed by heating at atmospheric pressure and the product distilled at reduced pressure. It boiled at about 110-113 C. at 25 mm.

' The condensation of -chloroindan with 5-. aminoindan' was then carried. out. About 40 parts by weight of 5-amin'oindan was heated to reflux temperature-with about 0.3 part of cupric chloride. About 3.2 parts of metallic sodium were added slowly over a period of about 40 minutes. There were then added about 26 parts of 5-chloroindan, and the mixture was refluxed for about minutes. After cooling to about 100 C., 50 parts of water were added rapidly, and the mixture was filtered. It was found that the addition of 50 parts of benzene facilitated the filtration greatly. After drying the filtrate, the benzene was removed by heating at atmospheric pressure, and the product was distilled at reduced pressure, boiling at about 170-180? C. at 1 mm. The product, a yellow oil, was found by analysis to have the compositioncalculated for di(5-indanamine).

Other N-aromatic substituted 5-aminoindans may be prepared by employing the appropriate 5-aminoindan and halogenated aromatic compound as starting materials.

In order to show the superiority of my new compounds as antioxidants, the following rub E longation Tensile None Lani lino indan fi-anilmo indan Other portions of the compositions were aged, 14 days in a Geer oven at 70 C. and flexed on a De-Mattia flexing machine at 80 F. at the rate Antioxidant No. flexures Rating 300, DC) 2, O00, 000 5, 000, 000

It is clear from these results that my new compounds are far superior to other compounds of the same general class. Similar results may be obtained when other N-aromatic-substituted 5- aminoindans are compared with N-aromatic-substituted aminoindans in which the amino group is attached to the indan nucleus at other positions.

In another example N-(p-isopropoxyphenyD- fi-indanamine was employed as the antioxidant in the rubber composition given above. The loss in tensile strength after aging 96 hours in oxygen at C. and 300 lbs. per sq. in. pressure was only about one-third as great as the loss in a similar composition containing no antioxidant. When flexed, after aging fourteen days ina Geer oven, the sample containing antioxidant resisted rupture about nine times as long as did the sample containing no antioxidant.

In a third example di-(5-indanamine) was employed as the antioxidant in the above composition. The loss in tensile strength of this composition after aging was only about one-half as great as the loss in a similar composition containing no antioxidant, and the former withstood about ten times as many flexures as the latter before reaching an index of '7.

My new compounds are effective in amounts ranging from 0.1 to 5% or more of the rubber composition. preservation of other organic substances which tend to deteriorate in the presence of air, such as fish oil, linseed oil, tung oil, gasoline containing unsaturates, and the like, but they are particularly valuable for use in rubber or synthetic rubber compositions. They are effective with any kind of rubber, such as caoutchouc, balata, guttapercha, latex, reclaimed rubber, artificial rubber isomers, and such synthetic rubbers as polychloroprene, copolymers of butadiene with acrylonitrile, styrene, methyl acrylate, methyl methacrylate, isobutylene, and other copolymerizable monomers. The term a rubber as used in the appended claims is intended to designate all of the above-mentioned materials.

My new antioxidants may be added to the material to be preserved in any suitable manner; they may be added in the form of a solution or emulsion or used in their pure form. They may be added to the rubber on a roll mill or in an internal mixer, or by any other suitable method.

They may be applied to the surface of the rub ber composition, either in their pure form or as a solution or paste, or they may be dispersed in the rubber latex. It is accordingly to be understood that the term treating" is employed in the 13- pended claims in a generic sense to embrace the incorporation of the antioxidant into the rubber by any of the above-described methods.

The rubber compositions containing my new antioxidants may be used for a variety of par:

poses, such as the manufacture of hose, bcltingj' rubber thread, rubberized fabrics, boots, shoes, molded goods, tires and inner tubes, latex dipped 5 goods, and the like.

They may also be used for the.

Any of the usual pigments, fillers, dyes, ac-

celerators of vulcanization, or other antioxidants may be used in conjunction with my new antioxidants without destroying the superior properties of the composition containing them.

Although I have herein disclosed specific examples of my invention, I do not intend to limit myself solely thereto, but to include all of the obvious variations and modifications within the scope of the appended claims.

I claim:

1. The method of preserving a rubber which comprises treating it with a compound of the structure R1-NHR2 in which R1 is an aromatic radical and R2 is an indan radical attached to the nitrogen at the 5-position, said compound being free from acidic groups.

2. The method of preserving rubber which comprises treating it with acompound of the structure R1-NH-R2 in which R1 is an aromatic radical and R2 is an indan radical attached to the nitrogen at the 5-position, said compound being free from acidic groups.

3. The method of preserving a rubber which comprises treating it with a 5-(arylamino) indan which is free from acidic groups.

4. The method of Preserving rubber which comprises treating it with a 5-(ary 1amino) indan which is free from acidic groups.

5. The method of preserving rubber which comprise treating it with 5-anilino indan.

6. The method of preserving rubber which comprises treating it with N-(p-isopropoxy phenyl)- 5-indanamine.

7. The method of preserving rubber which comprises treating it with di-(B-indanamine) 8. A composition comprising a rubber and a compound of the structure R1--NHRz in which B1 is an aromatic radical and R2 is an indan radical attached to the nitrogen at the 5-position, said compound being free from acidic groups.

9. A composition comprising rubber and a compound of the structure R1-NH-R2 in which R1 is an aromatic radical and R2 is an indan radical attached to the nitrogen at the 5-position, said compound being free from acidic groups.

10. A composition comprising a rubber and a S-(arylamino) indan which is free from acidic groups.

11. A composition comprising rubber and a 5- (arylamino) indan which is free from acidic groups.

12. A composition comprising rubber and 5- anilino indan.

13. A composition comprising rubber and N-' (p-isopropoxy phenyl) -5-indanamine.

14. A composition comprising rubber and di (5-indanamine) CARLIN F. GIBBS. 

